ggplotly() ignores function applied to fill labels

When passing a function to the labels argument of scale_fill_discrete(), ggplotly() does not apply this function to the labels. This works fine, however, when passing the same function to scale_x_discrete().

df <- data.frame(a = c("A", "B"), b = c(7, 9))

p <- ggplot(df, aes(a, b, fill = a)) +
  geom_col() +
  scale_x_discrete(labels = tolower) +
  scale_fill_discrete(labels = tolower)
p

plotly::ggplotly(p)

Start by running the provided R example with ggplotly(), comparing the scale_fill_discrete(labels = tolower) result with scale_x_discrete(labels = tolower). Trace how ggplotly() handles these two scale entry points; done means the fill labels are transformed by the supplied function in the interactive plot as the x labels are.